Cholesterol nucleation from its carriers in human bile

Area of Science:

• Hepatobiliary Science
• Lipid Metabolism
• Gastroenterology

Background:

• Biliary cholesterol crystallization is a key event in gallstone formation.
• The precise mechanism of cholesterol nucleation in bile remains incompletely understood.
• Bile contains cholesterol in both micellar and vesicular forms.

Purpose of the Study:

• To investigate whether biliary cholesterol primarily nucleates from vesicles or micelles.
• To determine the role of vesicles and micelles in the nucleation time of bile.

Main Methods:

• Analysis of gallbladder bile, hepatic bile, and model bile samples.
• Determination of nucleation times for whole bile and isolated vesicular/micellar fractions.
• Lipid composition analysis of bile samples.

Main Results:

• Cholesterol nucleated significantly faster from vesicles than micelles across all bile types.
• Biles without vesicles showed significantly slower nucleation times compared to those with vesicles.
• Nucleation time of bile strongly correlated with the nucleation time of its vesicular fraction, but not the micellar fraction.

Conclusions:

• Phospholipid vesicles are the predominant vehicle for cholesterol precipitation in bile.
• Vesicles play a critical role in determining the nucleation time of bile.
• Understanding vesicle-mediated nucleation is essential for insights into gallstone pathogenesis.